Preheat oven to 375° and grease or line your 8x8 baking pan.
Mix together flour, brown sugar, cinnamon, baking powder, baking soda, and salt until well combined.
Cut the butter into the mixture with a fork or pastry cutter until small crumbs form. Remove ¾ cup of the mixture for the topping and stir the pecans into the topping mixture. Set aside both mixtures.
In another bowl, whisk together the filling ingredients until smooth and set aside.
Press the crust mixture into the bottom of your prepared pan firmly in an even layer. Pour in the pumpkin filling and spread in an even layer. Sprinkle the pecan topping mixture over the pumpkin filling evenly.
Bake for 35 minutes in the preheat oven. Remove and allow to cool at room temperature for about 30 minutes, then place in the fridge for at least 2 hours to cool and set.
Remove from the fridge and slice into 16 bars. Serve or store in the fridge for up to 5 days!